*2.3. Methods*

#### 2.3.1. Evaluation of the PLEF of Land

The concept of the PLES is proposed based on the land use functions (LUFs). LUFs refer to the products and services provided for human society by land resources through various utilization methods [46,47]. Its concept can be traced back to the European Union's research on agricultural multifunction at the end of the 20th century [48,49]. The PLES is the extension of LUFs that the essence of PLES is a functional space divided according to the products and services it provides on the basis of LUFs [21]. Therefore, the logical connection between land use types and land use functions can be established to construct a scientific classification and evaluation system of the PLES [50]. Based on the research results of scholars and guided by the theory of the PLES, this study divided land use functions into production functions, living functions and ecological functions and divided land use types into production land, living land, and ecological land. According to the difference in the strength of the PLEF of land use, this study introduced the concepts of strong production/living/ecological land, semi-production/living/ecological land, and weak production/living/ecological land. Then, values were assigned to strong production/living/ecological land, semi-production/living/ecological land, and weak production/living/ecological land by using the method of grading assignment.

Taking production land as an example, strong production land means that the production function of land is stronger than other functions, so the assigned function score is up to 5 points. Semi-production land means that the production function of land use is roughly equivalent to other functions, so the assigned function score is up to 3 points. A weak production function means that the production function of land use is weaker than other functions, so 1 point is assigned. In addition, nonproduction land refers to land that does not have a production function and is assigned a value of 0. In this paper, strong/semi/weak production land only reflects the dominant function, not the actual performance of the land's output or the monetary value added per unit of land in terms of productivity. The assignment of living land and ecological land was the same as that of production land (Table 1). First, 300 m × 300 m geographic grids were built based on ArcGIS 10.2 software. Second, the area of each land use type in each geographic grid was counted. Third, the PLEF evaluation method was used to sum the functional scores of production land, living land, and ecological land in each geographic grid. Finally, the spatial distribution map of the production/life/ecological function scores was generated to reveal the distribution pattern of the PLES in the study area. The evaluation method of the PLEF is shown in Formula (1).

$$\mathcal{W}\_{\bar{i}} = \sum\_{i=1}^{n} \mathbb{S}\_{\bar{i}} \cdot V\_{\bar{i}} \tag{1}$$

In Formula (1), *Wi* refers to the evaluation score of the production/living/ecological function in each geographic grid. *i* is the land use type. *n* is the total number of land use types in each geographic grid. *Si* represents the area of each land use type in each geographic grid, and its unit is hm2. *Vi* represents the production/living/ecological function value of the unit area of the i-th land use type.


**Table 1.** Classification and function assignment of the PLEL of Jiangjin District in 2018.
